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| 型号： | LTC3407EDD#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 11/16页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 1A DL 10DFN |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 2 |
| 输出电压： | 0.6 V ~ 5 V |
| 输入电压： | 2.5 V ~ 5.5 V |
| PWM 型： | 电流模式，混合 |
| 频率 - 开关： | 1.5MHz |
| 电流 - 输出： | 1A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-WFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
LTC3407
APPLICATIONS INFORMATION
produce the most improvement. Percent ef?ciency can
be expressed as:
%Ef?ciency = 100% - (L1 + L2 + L3 + ...)
where L1, L2, etc. are the individual losses as a percent-
age of input power.
Although all dissipative elements in the circuit produce
losses, 4 main sources usually account for most of the
losses in LTC3407 circuits: 1)V IN quiescent current, 2)
switching losses, 3) I 2 R losses, 4) other losses.
1) The V IN current is the DC supply current given in the
Electrical Characteristics which excludes MOSFET driver
and control currents. V IN current results in a small (<0.1%)
loss that increases with V IN , even at no load.
2) The switching current is the sum of the MOSFET driver
and control currents. The MOSFET driver current results
from switching the gate capacitance of the power MOSFETs.
Each time a MOSFET gate is switched from low to high
to low again, a packet of charge dQ moves from V IN to
ground. The resulting dQ/dt is a current out of V IN that is
typically much larger than the DC bias current. In continu-
ous mode, I GATECHG = f O (Q T + Q B ), where Q T and Q B are
the gate charges of the internal top and bottom MOSFET
switches. The gate charge losses are proportional to V IN
and thus their effects will be more pronounced at higher
supply voltages.
3) I 2 R losses are calculated from the DC resistances of the
internal switches, R SW , and external inductor, R L . In con-
tinuous mode, the average output current ?owing through
inductor L, but is “chopped” between the internal top and
bottom switches. Thus, the series resistance looking into
the SW pin is a function of both top and bottom MOSFET
R DS(ON) and the duty cycle (DC) as follows:
R SW = (R DS(ON)TOP )(DC) + (R DS(ON)BOT )(1 – DC)
The R DS(ON) for both the top and bottom MOSFETs can
be obtained from the Typical Performance Characteristics
curves. Thus, to obtain I 2 R losses:
I 2 R losses = (I OUT ) 2 (R SW + R L )
4) Other ‘hidden’ losses such as copper trace and internal
battery resistances can account for additional ef?ciency
degradations in portable systems. It is very important
to include these “system” level losses in the design of a
system. The internal battery and fuse resistance losses
can be minimized by making sure that C IN has adequate
charge storage and very low ESR at the switching frequency.
Other losses including diode conduction losses during
dead-time and inductor core losses generally account for
less than 2% total additional loss.
Thermal Considerations
In a majority of applications, the LTC3407 does not dis-
sipate much heat due to its high ef?ciency. However, in
applications where the LTC3407 is running at high ambient
temperature with low supply voltage and high duty cycles,
such as in dropout, the heat dissipated may exceed the
maximum junction temperature of the part. If the junction
temperature reaches approximately 150°C, both power
switches will be turned off and the SW node will become
high impedance.
To prevent the LTC3407 from exceeding the maximum
junction temperature, the user will need to do some thermal
analysis. The goal of the thermal analysis is to determine
whether the power dissipated exceeds the maximum
junction temperature of the part. The temperature rise is
given by:
T RISE = P D ? θ JA
where P D is the power dissipated by the regulator and θ JA
is the thermal resistance from the junction of the die to
the ambient temperature.
The junction temperature, T J , is given by:
T J = T RISE + T AMBIENT
As an example, consider the case when the LTC3407 is
in dropout on both channels at an input voltage of 2.7V
with a load current of 600mA and an ambient temperature
of 70°C. From the Typical Performance Characteristics
graph of Switch Resistance, the R DS(ON) resistance of
the main switch is 0.425Ω. Therefore, power dissipated
by each channel is:
P D = I OUT2 ? R DS(ON) = 153mW
The MS package junction-to-ambient thermal resistance,
θ JA , is 45°C/W. Therefore, the junction temperature of
3407fa
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| LTC3407EMSE | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC3407EMSE#PBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC3407EMSE#TR | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC3407EMSE#TRPBF | 功能描述:IC REG BUCK SYNC ADJ 1A 10MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC3407EMSE-2 | 制造商:Linear Technology 功能描述:Conv DC-DC Dual Step Down 2.5V to 5.5V 10-Pin MSOP EP |
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